ABSTRACTAsymmetric dimethylarginine (ADMA) is synthesized by protein arginine methyltransferases during methylation of protein arginine residues and released into blood upon proteolysis. Higher concentrations of ADMA in blood have been observed in patients with metabolic diseases and certain cancers. However, the role of ADMA in colon cancer has not been well investigated. ADMA serum levels in human patients diagnosed with colon cancer were found to be higher than those present in healthy subjects. ADMA treatment of LoVo cells, a human colon adenocarcinoma cell line, attenuated serum starvation-induced apoptosis and suppressed the activation of the Fas (APO-1/CD95)/JNK (SAPK) (c-Jun N terminal protein kinase/stress-activated protein kinase)pathway. ADMA also suppressed the activation of JNK triggered by death receptor ligand anti-Fas mAb and exogenous C2-ceramide. Moreover, we demonstrated that ADMA pretreatment protected LoVo cells from doxorubicin hydrochloride-induced cell death and activation of the Fas/JNK pathway. In summary, our results suggest that the elevated ADMA in colon cancer patients may contribute to the blocking of apoptosis of cancer cells in response to stress and chemotherapy.

fig3: ADMA inhibited serum starvation-induced apoptosis and the Fas/JNK pathway in LoVo cells. LoVo cells were cultured in control or serum-free media in the presence or absence of 10 μM ADMA for 96 h. (a) The apoptosis rate was assayed using flow cytometry after staining with Annexin V-FITC and propidium iodide. (b) Statistical results of apoptosis in different cell groups. (c) Western blot analysis of Fas/JNK pathway proteins as indicated. Data are presented as mean±S.E., and are representative of two independent experiments performed in triplicate. The statistical significance was calculated with Student's t-test. C: control media (10% FBS DMEM); SS: serum starvation

Mentions:
Tumor cells usually undergo increased apoptosis during SS;17, 18 therefore, we hypothesized that ADMA might inhibit SS-induced apoptosis in LoVo cells. To test this hypothesis, we measured the apoptosis rate of LoVo cells treated with or without 10 μM ADMA for 96 h in serum-free media using flow cytometry. We found that the apoptosis rate was almost doubled upon SS compared to control cells cultured in 10% FBS DMEM. Furthermore, ADMA treatment significantly suppressed the apoptosis induced by SS (Figures 3a and b).

fig3: ADMA inhibited serum starvation-induced apoptosis and the Fas/JNK pathway in LoVo cells. LoVo cells were cultured in control or serum-free media in the presence or absence of 10 μM ADMA for 96 h. (a) The apoptosis rate was assayed using flow cytometry after staining with Annexin V-FITC and propidium iodide. (b) Statistical results of apoptosis in different cell groups. (c) Western blot analysis of Fas/JNK pathway proteins as indicated. Data are presented as mean±S.E., and are representative of two independent experiments performed in triplicate. The statistical significance was calculated with Student's t-test. C: control media (10% FBS DMEM); SS: serum starvation

Mentions:
Tumor cells usually undergo increased apoptosis during SS;17, 18 therefore, we hypothesized that ADMA might inhibit SS-induced apoptosis in LoVo cells. To test this hypothesis, we measured the apoptosis rate of LoVo cells treated with or without 10 μM ADMA for 96 h in serum-free media using flow cytometry. We found that the apoptosis rate was almost doubled upon SS compared to control cells cultured in 10% FBS DMEM. Furthermore, ADMA treatment significantly suppressed the apoptosis induced by SS (Figures 3a and b).

ABSTRACTAsymmetric dimethylarginine (ADMA) is synthesized by protein arginine methyltransferases during methylation of protein arginine residues and released into blood upon proteolysis. Higher concentrations of ADMA in blood have been observed in patients with metabolic diseases and certain cancers. However, the role of ADMA in colon cancer has not been well investigated. ADMA serum levels in human patients diagnosed with colon cancer were found to be higher than those present in healthy subjects. ADMA treatment of LoVo cells, a human colon adenocarcinoma cell line, attenuated serum starvation-induced apoptosis and suppressed the activation of the Fas (APO-1/CD95)/JNK (SAPK) (c-Jun N terminal protein kinase/stress-activated protein kinase)pathway. ADMA also suppressed the activation of JNK triggered by death receptor ligand anti-Fas mAb and exogenous C2-ceramide. Moreover, we demonstrated that ADMA pretreatment protected LoVo cells from doxorubicin hydrochloride-induced cell death and activation of the Fas/JNK pathway. In summary, our results suggest that the elevated ADMA in colon cancer patients may contribute to the blocking of apoptosis of cancer cells in response to stress and chemotherapy.